The invention concerns a computer system for data administration, with memory means storing at least one data field.
In such database systems, all the data items are stored in tabular data fields. Thus, for example, each row of a customer table contains a consecutive customer number, the name and the address of the customer, etc. A second table stores any deliveries the customer has previously received. Each row of the latter table contains the customer number to which deliveries have been made, as well as the respective date of delivery, the name and the quantity of the delivered article, etc. In the described example, both tables are linked by the customer number. The query as to which deliveries a customer x received on a particular date y is answered by the database in that initially the number associated with customer x is determined, and that the second table is searched for the total number of deliveries stored under his customer number and which, in addition, were made on the specified date y. New customers may subsequently be stored in the table at any time. Similarly, the second table may be updated on deliveries made.
However, subsequent changes in the database structure, if at all possible, necessitate revising the applications based thereon. This means that when the tables are drawn up, any potential requirements, in particular those to be met by the database, must be considered. If, in addition to the afore-mentioned data, the described customer table is to comprise, for example, a BTX number for each customer, a new table has to be prepared in which each customer number is associated with a BTX number. The customer numbers which have to be repeated for this purpose require an almost intolerable amount of memory space in particular in large databases. To avoid wasting memory space in that way, the customer table has to be supplemented by a further column with the BTX numbers. However, this is very expensive and time-consuming, as it entails changing a major part of the stored data and application programs.
It is the object of the invention to provide a computer system for data administration, wherein structural changes may be easily made.